Stroke is a serious and life threatening disease. About 85% of all strokes are ischemic, caused by a blood clot or plaque that blocks a blood vessel in the brain. The thrombolytic drug tissue plasminogen activator (tPA) is the only early treatment for acute ischemic stroke approved by the FDA. Treatment with tPA must be administered within three hours of the stroke onset. Furthermore, tPA treatment carries a recognized risk of bleeding in the brain. GM602 is an investigational drug that may act as a neuroprotectant in patients who have had a stroke. It is thought to stop cell death and reduce inflammation in the injured area of the brain. This study is designed to evaluate the safety and efficacy of GM602 administered intravenously to patients in three consecutive daily doses of 320 mg/dose or 480 mg/dose, the initial dose administered within 18 hours after onset of acute ischemic stroke in the Middle Cerebral artery region.